The work of this laboratory has centered around the following aspects of carotid body function: 1) Biophysics of the membrane of type I cells; 2) trophic influences of these cells on chemoreceptor function and influences of the carotid nerve on the function of these cells; 3) renewed efforts to understand the transduction process between cells and nerve endings; and 4) comparative studies on the function and pharmacology of carotid chemoreceptors of cat and rabbit. 1) Glomus cells of cat are very sensitive to temperature changes being depolarized (with a decreased input resistance) by cold and hyperpolarized with an increased input resistance by heat; also, hyperosmolarity depolarizes these cells with a decreased input resistance and hypo-osmolarity has the opposite effects. 2) Glomus cells are essential for chemoreception; if they are destroyed by ischemia and the nerves survive, chemoreceptive properties are lost. The carotid nerve appears important in maintaining proper cell functions. 3) A study of transduction between cells and nerve endings has proven to be difficult. Efforts are being made to develop a different preparation. 4) Comparative studies of cat and rabbit carotid bodies have shown that the two species have very different pharmacological problems. Carotid nerve discharges in cat are depressed by dopamine and excitedby ACh. In the rabbit, dopamine stimulates while ACh depresses the discharges. This depression is followed by excitation. ACh-induced depression in rabbits is mediated via muscarinic receptors. ACh-induced excitation in these species appears to be nicotinic. In cats, excitation induced by ACh is nicotinic and no muscarinic effects have been found. Work continues along these lines.